http://www.biology-online.org/dictionary/Vesicle defines a vesicle as follows: A small cyst or sack containing gas or fluid.
In cell biology it defines a bubble-like membranous structures that stores and transports cellular products and digests metabolic wastes within the cell.
In physiology it’s a membranous pouch within an axon terminal that stores and releases neurotransmitters.
In phycology it means a floating gas-filled bubble or bladder-like structure in algal cells.
Mycology defines a vesicle as a bubble-like sack in fungus where zoospores mature and are eventually released
In pathology it is known as a small fluid-filled lesion or blister beneath the skin.